The explanation pertains to electronic circuits that are made up of semiconductor devices, for example, digital signal processors (DSPs), microprocessors, memory circuits, etc.
Various attempts have been made to miniaturize semiconductor devices and to increase their operating speed. However, an obstacle to changing to high-speed operation in these types of circuits is the signal propagation delays of the signal lines.
The signal propagation delay of signal lines is mainly due to the wiring resistance of the semiconductor device, for example, a metal film semiconductor device (MOS device), and the wiring capacitance (electrostatic wiring capacitance).
The main factor controlling the electrostatic wiring capacitance in manufacturing processes of up to about 0.8 .mu.m is the electrostatic capacitances between the wires and the semiconductor substrate. However, accompanying progress in miniaturization, the distance between adjacent wires in the semiconductor device has been greatly reduced, the electrostatic capacitance between adjacent wires is impossible to ignore, and in manufacturing processes of 0.6 .mu.m and below, when the wiring is formed with minimum spacing, the electrostatic capacitance between adjacent wires accounts for more than 90% of the total electrostatic capacitance.
Crosstalk has increased due to the increase in electrostatic capacitance between wires. The increase in crosstalk increases the signal delay. Such signal delays that result from crosstalk are the cause of various problems.
For example, when crosstalk occurs in the clock wiring, there are instances when deterioration of performance occurs that results from the delay of the clock, and there is the possibility that with a two phase clock, skewing (phase offset) between the two phase clocks occurs.
Also, if crosstalk occurs in a bus line, the delay due to the crosstalk will limit the operating speed of the IC. That is, the crosstalk will determine the operating speed of the IC.
In other electronic circuits problems also occur, such as skewing, lowering the operating speed, and operating errors due to distortion of the pulse signal, which originate with crosstalk in the same manner.
In general, there have been various attempts to prevent this type of crosstalk. For example, in one method the distance between adjacent wires is increased, but this method cannot be applied to semiconductor devices and semiconductor circuits in which miniaturization has advanced since the surface area increases.
As another general method, there is the method that adopts barriers (shields). However, if shields are implemented, the surface area becomes a problem. The fact that new area is required for implementation of shields makes this method inapplicable to the semiconductor devices and Ics whose fineness and integration level are required to be further improved.
Therefore, the present invention offers a circuit wherein the crosstalk can be reduced or eliminated with a method that does not affect improvements in miniaturization or the integration level.